The proposed research focuses on the communication of information about illness from physicians to patients. The particular question of interest is: What criteria do physicians use in determining the information about illness they convey to patients? Information transmittal is important in clinical medicine because of its relationships to history-taking, medical records, patients' compliance and satisfaction, and physiologic response to therapy. The informative process in medicine also extends the sociological problems of uncertainty and power; it is hypothesized that a physician's ability to preserve his own power depends largely on his control of the patient's uncertainty. Principles from information theory, sociolinguistics and ethnomethodology are applicable to the research problems. OBJECTIVES: The following methods have been used to study the informative process in medicine: participant observation; experimental communications; questionnaires and interviews; the case-study method; and the direct recording analysis of doctor-patient interaction. The latter technique, employed in the proposed research, offers the greatest potential for valid conclusions about the informative process. A multivariate research model of the informative process has been developed. The over-all objective of the research is to use this model in studying the association between transmitted information (the dependent variable) and several independent variables, which are outlined under the headings of physician characteristics, patient characteristics, and situational characteristics. METHODS: The methods involve the direct recording and analysis of doctor-patient interaction. There are four ways by which the dependent variable is measured from tape recordings and transcripts: time measures, measures of information, measures of level of explanation, and qualitative analysis. Independent variables are measured by questionnaires and interviews administered to physicians and patients. The total sample includes three samples: 1) physicians who work in both outpatient clinics and private practice; 2) private practitioners unassociated with university hospitals; and 3) physicians in a clinic whose interaction with patients is followed longitudinally over time. Non-verbal communication is studied by video tapes.